It is currently known to use a hollow tubular cannula to provide access for a physician to an internal area in a patient. The cannula essentially provides a stable, versatile lumen into the area to be examined or treated. Examination tools, such as endoscopes, can be inserted and withdrawn through the cannula as required. Similarly, surgical instruments or other treatment equipment can be inserted or withdrawn, all without undue trauma to the skin, muscle tissue or other intervening tissue. Cannulae are used for this purpose in order to provide access to the internal area with a minimum of trauma to the intervening tissues, and similarly, the number of cannulae used is held to a minimum.
The means of inserting a cannula is illustrated in FIG. 1, where the cannula 10 is first fitted onto an insertion tool or trocar 13, leaving a sharp point or other cutting contour projecting beyond the distal end 11 of cannula 10. Fitting cannula 10 onto trocar 13 essentially converts them to a single tool for establishing an access passageway into an internal area of the patient 16. The trocar 13 provides the necessary cutting contour and the desired stiffness to facilitate proper insertion of the tools. This is accomplished by inserting the trocar and cannula combination into a puncture 14 in the skin, and continuing on into patient 16 until the distal end 11 of cannula 10 reaches the desired area to be examined or treated.
This insertion process involves the skillful maneuvering of the cutting contour of trocar 13 around and through intervening tissues. The exact path followed will depend not only on the location of puncture 14, but also on the location, configuration, and condition of any intervening tissues. For instance, the path followed through intervening muscle tissue will necessarily pass between certain muscle fibers, depending upon the path chosen by the physician. Insertion of a given cannula at a given location, with a given target, will be able to follow several slightly different paths. After insertion of the trocar 13 and cannula 10, as shown in FIG. 1, trocar 13 is withdrawn from patient 16 through cannula 10, leaving cannula 10 in place in the passageway chosen by the physician, as shown in FIG. 2. Puncture wound 14 in the skin and some of the intervening tissues will, to some extent, close around and conform to cannula 10. Other intervening tissues or organs will, of course, remain clear of the passageway as long as cannula 10 remains in place. Even though examination and treatment via the cannula 10 will minimize trauma to the surrounding tissues, it can be seen that creation of this passageway causes some trauma to the intervening tissues, so creation of additional passageways is to be minimized.
From time to time, it becomes necessary to replace an existing cannula with a different cannula serving the same internal area. This can be required, for example, if the replacement cannula has a larger diameter than the existing cannula, allowing insertion of larger tools, or additional tools, or allowing performance of a different examination or treatment procedure. It is also possible that a replacement cannula might offer other features different from the existing cannula besides diameter. Unfortunately, installation of a replacement cannula in place of an existing cannula currently requires the withdrawal of the existing cannula, followed by insertion of the replacement cannula.
When the existing cannula is withdrawn, the skin and other intervening tissues can close into the established passageway, and internal organs can move into the passageway. This results in the partial or complete disappearance of the passageway, requiring the physician to insert the replacement cannula, with a conventional trocar, into the same puncture. In most cases, the path followed by the insertion of the replacement cannula will not be identical to the path followed by the first cannula. This results in additional trauma to the intervening tissues, accompanied by possible additional post-operative soreness or additional scar tissue. It also requires additional time to withdraw the cannula and to attempt to follow the original passageway with the replacement cannula.
It would be desirable to have a method and apparatus which would allow the replacement of an existing cannula with a different cannula, following the same passageway as that followed by the existing cannula. It is the object of this invention to provide an apparatus which can be inserted through an existing cannula, allowing removal of the cannula and insertion of a trocar along the original passageway. It is a further object of this invention to provide a rod which can be inserted through an existing cannula and anchored in place, allowing removal of the existing cannula over the rod, followed by insertion of a trocar with a new cannula, through the original passageway. It is a further object of this invention to provide a method for inserting a guide rod through an existing cannula, anchoring the rod in place, removing the existing cannula, and insertion of a replacement cannula through the original passageway. Finally, it is an object of this invention to provide a method and apparatus for replacement of a cannula, which are relatively cost effective and easy to operate.